Add support invoke-polymorphic to dexdump

o Update bytecode.txt with codepoints for invoke-polymorphic
  instructions and run opcode-gen/regen-all.

o Update dexdump to support invoke-polymorphic with output equivalent to
  dexdump2.

o Add format classes to dexgen and dx.

Bug: 30550796
Test: manually tested with DEX files generated from ART run-tests.
Change-Id: I986a896747d73e11418ba1876cce86087b4a9e68